require 'uri'
require 'time'
require 'json'
require 'psych'
require 'pathname'
require 'open-uri'

require 'openapi_parser/version'
require 'openapi_parser/config'
require 'openapi_parser/errors'
require 'openapi_parser/concern'
require 'openapi_parser/schemas'
require 'openapi_parser/path_item_finder'
require 'openapi_parser/request_operation'
require 'openapi_parser/schema_validator'
require 'openapi_parser/parameter_validator'
require 'openapi_parser/reference_expander'

module OpenAPIParser
  class << self
    # Load schema hash object. Uri is not set for returned schema.
    # @return [OpenAPIParser::Schemas::OpenAPI]
    def parse(schema, config = {})
      load_hash(schema, config: Config.new(config), uri: nil, schema_registry: {})
    end

    # @param filepath [String] Path of the file containing the passed schema.
    #   Used for resolving remote $ref if provided.
    #   If file path is relative, it is resolved using working directory.
    # @return [OpenAPIParser::Schemas::OpenAPI]
    def parse_with_filepath(schema, filepath, config = {})
      load_hash(schema, config: Config.new(config), uri: filepath && file_uri(filepath), schema_registry: {})
    end

    # Load schema in specified filepath. If file path is relative, it is resolved using working directory.
    # @return [OpenAPIParser::Schemas::OpenAPI]
    def load(filepath, config = {})
      load_uri(file_uri(filepath), config: Config.new(config), schema_registry: {})
    end

    # Load schema located by the passed uri. Uri must be absolute.
    # @return [OpenAPIParser::Schemas::OpenAPI]
    def load_uri(uri, config:, schema_registry:)
      # Open-uri doesn't open file scheme uri, so we try to open file path directly
      # File scheme uri which points to a remote file is not supported.
      content = if uri.scheme == 'file'
        open(uri.path)&.read
      elsif uri.is_a?(OpenURI::OpenRead)
        uri.open()&.read
      end

      extension = Pathname.new(uri.path).extname
      load_hash(parse_file(content, extension), config: config, uri: uri, schema_registry: schema_registry)
    end

    private

      def file_uri(filepath)
        path = Pathname.new(filepath)
        path = Pathname.getwd + path if path.relative?
        URI.join("file:///",  path.to_s)
      end

      def parse_file(content, ext)
        case ext.downcase
        when '.yaml', '.yml'
          parse_yaml(content)
        when '.json'
          parse_json(content)
        else
          # When extension is something we don't know, try to parse as json first. If it fails, parse as yaml
          begin
            parse_json(content)
          rescue JSON::ParserError
            parse_yaml(content)
          end
        end
      end

      def parse_yaml(content)
        # FIXME: when drop ruby 2.5, we should use permitted_classes
        (Gem::Version.create(RUBY_VERSION) < Gem::Version.create("2.6.0")) ? 
          Psych.safe_load(content, [Date, Time]) : 
          Psych.safe_load(content, permitted_classes: [Date, Time])
      end

      def parse_json(content)
        JSON.parse(content)
      end

      def load_hash(hash, config:, uri:, schema_registry:)
        root = Schemas::OpenAPI.new(hash, config, uri: uri, schema_registry: schema_registry)

        OpenAPIParser::ReferenceExpander.expand(root, config.strict_reference_validation) if config.expand_reference

        # TODO: use callbacks
        root.paths&.path&.values&.each do | path_item |
          path_item.set_path_item_to_operation
        end

        root
      end
  end
end